CVE-2026-31976Known exploitationPublic exploitNetwork attack vector

CI runner command execution via poisoned tag

Published Mar 11, 2026 · Updated Mar 11, 2026

Supply-chain compromise in Xygeni xygeni-action v5 allows remote attackers to execute commands on CI runners through a poisoned tag. The mutable v5 tag was redirected to an unmerged action.yml commit whose disguised telemetry step registered the runner with a C2 server, polled for commands, passed them to eval, and exfiltrated compressed output. Exposure required a workflow run referencing @v5 from March 3 through March 10, 2026; each run gave the attacker command execution for up to 180 seconds and access to runner-available data.

CVSS severity9.3
Critical
EPSS probability0.50%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Supply-chain compromise in Xygeni xygeni-action v5 allows remote attackers to execute commands on CI runners through a poisoned tag. The mutable v5 tag was redirected to an unmerged action.yml commit whose disguised telemetry step registered the runner with a C2 server, polled for commands, passed them to eval, and exfiltrated compressed output. Exposure required a workflow run referencing @v5 from March 3 through March 10, 2026; each run gave the attacker command execution for up to 180 seconds and access to runner-available data.

The record

CVE
CVE-2026-31976
Published
Mar 11, 2026
Updated
Mar 11, 2026
Vendor
Xygeni
Product
xygeni-action
Classifications
CWE-506, T1059.004, T1195.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 3, 2026Exploitation reportedxygeni-action v5 tag-poisoning incident
  2. Mar 11, 2026CVE publishedPublication date reported by the CVE source.
  3. Mar 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= March 3, 2026, <= March 10, 2026

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Xygeni · xygeni-actionversion=>= March 3, 2026, <= March 10, 2026

Published CVSS scores

9.3GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-506Embedded Malicious Code
T1059.004Unix Shell
T1195.002Compromise Software Supply Chain

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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